Thursday, June 8, 2017

Even moderate drinking linked to a decline in brain health

Alcohol consumption, even at moderate levels, is associated with
increased risk of adverse brain outcomes and steeper decline in
cognitive (mental) skills, finds a study published by The BMJ today.
These results support the recent reduction in alcohol guidance in
the UK and raise questions about the current limits recommended in the
US, say the authors.

Heavy drinking is known to be associated with poor brain health, but
few studies have examined the effects of moderate drinking on the brain
-- and results are inconsistent.

So a team of researchers based at the University of Oxford and
University College London set out to investigate whether moderate
alcohol consumption has a beneficial or harmful association -- or no
association at all -- with brain structure and function.

They used data on weekly alcohol intake and cognitive performance
measured repeatedly over 30 years (1985-2015) for 550 healthy men and
women who were taking part in the Whitehall II study.
This study is evaluating the impact of social and economic factors on the long term health of around 10,000 British adults.

Participants had an average age of 43 at the start of the study and
none were alcohol dependent. Brain function tests were carried out at
regular intervals and at the end of the study (2012-15), participants
underwent an MRI brain scan.
Several factors that could have influenced the results (known as
confounding) were taken into account, such as age, sex, education,
social class, physical and social activity, smoking, stroke risk and
medical history.

After adjusting for these confounders, the researchers found that
higher alcohol consumption over the 30 year study period was associated
with increased risk of hippocampal atrophy - a form of brain damage that
affects memory and spatial navigation.

While those consuming over 30 units a week were at the highest risk
compared with abstainers, even those drinking moderately (14-21 units
per week) were three times more likely to have hippocampal atrophy
compared with abstainers.

There was no protective effect of light drinking (up to 7 units per week) over abstinence.

Higher consumption was also associated with poorer white matter
integrity (critical for efficient cognitive functioning) and faster
decline in language fluency (how many words beginning with a specific
letter can be generated in one minute).

But no association was found with semantic fluency (how many words
in a specific category can be named in one minute) or word recall.

The authors point out that this is an observational study, so no
firm conclusions can be drawn about cause and effect, and say some
limitations could have introduced bias. However, key strengths include
the information on long term alcohol consumption and the detailed
available data on confounding factors.

As such, they say their findings have important potential public health implications for a large sector of the population.

"Our findings support the recent reduction in UK safe limits and
call into question the current US guidelines, which suggest that up to
24.5 units a week is safe for men, as we found increased odds of
hippocampal atrophy at just 14-21 units a week, and we found no support
for a protective effect of light consumption on brain structure," they
write.

"Alcohol might represent a modifiable risk factor for cognitive
impairment, and primary prevention interventions targeted to later life
could be too late," they conclude.

In a linked editorial, Killian Welch, consultant neuropsychiatrist
at the Royal Edinburgh Hospital, says these findings "strengthen the
argument that drinking habits many regard as normal have adverse
consequences for health."

This is important, he adds. "We all use rationalisations to justify
persistence with behaviours not in our long term interest. With
publication of this paper, justification of "moderate" drinking on the
grounds of brain health becomes a little harder."